1. Field of the Invention
The present invention relates to a clam-shell shaped image forming apparatus with a movable document plate, particularly to a plate-position determination device setting the position of the document plate to the fixed position on an upper body of the apparatus when the upper body is opened.
2. Description of the Prior Art
A copying machine will be shown in FIG. 2 (a) and ibid. (b) as an example of the above-said kind of the image forming apparatus. When an upper body 2 of the copying machine will be opened in the direction of the arrow 3 from a lower body 1 as the standard, a document plate 6 provided movably toward the arrow 4, 5 on the upper body 2 must have been moved to the fixed position on the upper body 2 in advance, i.e., an edge portion 6a of the document plate 6 must have been in the area shown by the hatching 7 on the top face of the upper body 2.
But for the movement of the document plate 6 as mentioned above, a paper-feed section 8 or the document plate 6 might be damaged owing to the collision of the document plate 6 against the paper-feed section 8 installed at the side of the lower body 1 of the copying machine if the upper body 2 is opened and closed with the document plate 6 in a position except one fixed on the upper body 2. In addition, the document plate 6 might be damaged due to pressing down on its top face with operator's hand with the document cover therebetween.
Accordingly above-said copying machine should be comprised as the upper body 2 can be opened by means of the operation of the release lever (as not shown in Fig.) provided in a cover 9 only when the movement for the document plate 6 is fixed in position on the upper body 2 in advance.
As for the conventional copying machine as stated above, a position mark 10 forms at a position equivalent to the part shown by the hatching 7 on the top face of the upper body 2 below the under face of the document plate 6. So the document plate 6 finishes moving to the fixed position on the upper body 2 owing to the stop of the edge portion 6a of the document plate 6 at the position corresponding to the area of the position mark 10 after movement of it in the direction of the arrow 4 or the arrow 5 by an operator.
Now the document plate 6 should stop a the undefined position on the upper body 2 when there is a necessity for the upper body 2 to be opened in order that the jammed papers will be disposed after the paper jam occurs in the body of the copying machine. For example, the position mark 10 on the upper body 2 will become visible from the outside due to its exposure when the document plate 6 stops at the completion of movement in the direction of the arrow 5. Therefore an operator can make the document plate 6 move easily to a position wherein the edge portion 6a corresponds to the area of the position mark 10.
However the operator cannot notice the position mark 10 from the outside owing to the covering of the document plate 6 over the position mark 10 on the upper body 2 in case that the document plate 6 will stop in the condition of completion of movement in the direction of the arrow 4..
So the operator puts the position mark 10 in the visible condition from the outside by making the document plate 6 move in the direction of the arrow 5 in the first place for the purpose of the movement of the document plate 6 to the fixed position on the upper body 2. Next the operator must align the document plate 6 with the fixed position on the upper body 2 by means of the movement of the document plate 6 in the direction of the arrow 4. For that reason, it causes a problem in that the handling during opening of the upper body 2 is very inconvenient with regard to the foregoing copying machine.